1. Field of the Invention
The invention relates to a coolant amount determining apparatus which determines the amount of engine coolant.
2. Description of the Related Art
Japanese Patent Application Publication No. 2005-76483 (JP-A-2005-76483), for example, describes a cooling system which cools an engine by supplying coolant to the engine using a mechanical water pump driven by the engine.
The amount of coolant supplied for cooling the engine can be checked by checking the amount of coolant stored in a reservoir tank that is arranged in the coolant circulation path. However, because the reservoir tank is housed in the engine compartment or the like, it is necessary to open the engine compartment when checking the coolant amount, which makes checking the coolant amount extremely bothersome.
On the other hand, when there is an insufficient amount of coolant, an excessive rise in the coolant temperature can be determined by a temperature gauge that monitors the coolant temperature detected by known coolant temperature detecting means. However, the accuracy with a temperature gauge that simply monitors the temperature of the coolant detected by the coolant temperature detecting means is low. Moreover, the mechanical water pump is normally driven when the engine is running, so coolant that is discharged from this water pump is constantly in contact with the sensor portion of the coolant temperature detecting means. As a result, the degree of change in the coolant temperature detected by the coolant temperature detecting means is flat with little fluctuation. Therefore, with a temperature gauge that has low accuracy and which simply monitors the temperature of coolant that is detected by the coolant temperature detecting means, it. is difficult to recognize an excessive rise in the coolant temperature. Therefore, even if it becomes clear that the coolant amount is insufficient when an excessive rise in coolant temperature is recognized, the engine may already be overheating so it is not possible to prevent the engine from overheating.